Taximeters are devices disposed in taxis to determine a fare to be billed from a customer, i.e. passenger, at the end of a journey based on a number of factors such as distance traveled (e.g. X EUR per kilometer) and/or time elapsed (e.g. Y EUR per hour) since the taxi was assigned to the journey or picked up the customers. Further factors such as day of the week, time of day, waiting time, number of passengers, luggage, advance booking, departure location (e.g. airport), special assistance provided, etc. may also be taken into account in the overall pricing of the trip.
Part of the factors affecting the trip price may be determined by the taximeter in isolation, i.e. independently, responsive to e.g. a button press by the driver indicative of appropriate tariff or other relevant circumstances such as luggage type or departure location, whereas the remaining factors are obtained based on data received from the vehicle itself regarding e.g. the speed of the vehicle. An intermediate, officially approved conversion device, or ‘signal generator’, may be utilized to convert CAN (controller area network) bus data or corresponding data indicative of vehicle speed or distance to pulses understood by the taximeter in accordance with a predefined standard applied.
Sometimes, both distance traveled and time elapsed are applied simultaneously to determine the fare, which may be called as a ‘double’ type application of tariff. Alternatively, both charging criteria may be subjected to the same journey but only alternately, which may be referred to as ‘single’ type application of tariff. Taxi fares are usually more or less strictly regulated by the authorities depending on the country. Accordingly, the taximeters are often to be sealed subsequent to calibration so that related tampering becomes impossible without breaking the seal or other clearly visible part such as a housing thereof.
In addition to keeping track of the fare, the taximeters may comprise or be connected to various other features such as a receipt printer, a communication means, a positioning means, sensors, reporting/logging and payment features.
In terms of UI (user interface) features to enable the driver to interact with the device, the taximeters typically comprise a number of buttons and a display such as a simple LCD (liquid crystal display) type digital readout. A unit incorporating both the display and data input means may be provided with a dedicated housing separated from a main unit with electrical cabling interconnecting the two. The UI unit is located in the vehicle so as to enable the passenger(s) to inspect the read-out during the ride. Often this means upper central position relative to the dashboard, which, on the other hand, causes additional discomfort to the actual device user, i.e. taxi driver, who should be able to control the settings of the rides by operating the user input means such as switches or buttons thereof potentially several times even during a single trip.
In European Union (EU), a so-called Measuring Instruments Directive (MID) and associated annex MI-007 stipulate essential requirements for the taximeters throughout the EU. Having regard to the directive, the taximeters shall calculate and display the fare, incrementing in steps that may be fixed or generally regulated by the particular member state of the EU in question. The step, or ‘stroke’ (sometimes also ‘drop’), may correspond to some fixed value (amount), e.g. 0.20 EUR or 0.10 EUR, while the interval between successive strokes depends on the vehicle speed and/or time elapsed, as being contemplated above so that the predetermined pricing model such as distance-based pricing is still followed.
The stroke value and interval appear a clear trade-off between a) the perception ability of the passengers and related psychological aspects, and b) the actual accuracy of the fare-determining logic technologically achievable in the taximeter.
Modern measurement and data processing technology would easily provide to for the usage of stroke values with considerably finer resolution in terms of the used currency, e.g. one cent (c) increment in the total fare. However, that could result in basically continuously rolling or changing digits on the display of the taximeter especially when the speed of the vehicle increases, which would, in turn, complicate perceiving the current fare of the ride and appear psychologically generally suspicious to the passengers. Determination of the fare as executed by the taximeter would then seem vague if not directly fraudulent.
Nevertheless, the contemporary practice with the relatively large stroke values causes unavoidable financial losses to the taxi operator as at the end of the journey the ongoing, still unfinished, stroke period cannot be charged from the passenger(s) and the stroke shall be completely omitted. The accrued fare is thus rounded down to the latest amount indicated by the taximeter, still including the effect of a previous stroke completed but not the ongoing stroke. The problem may first seem somewhat negligible but the annual effect thereof is nothing but surprising. Considering e.g. a stroke size of 20 cents, average loss per journey can be estimated to be around 10 cents, which equals to 500 Euros annually with 5000 taxi drives.